The performance of an internal combustion engine can be optimized by adjusting the characteristics of its intake manifold as a function of the engine's operating condition. The characteristics of an intake manifold, such as its geometry, can be adjusted with one or more valves, such as charge motion control valves and resonance valves. Thus the performance of an international combustion engine can be optimized by controlling the valves of the engine's intake manifold.
Currently, the valves of an intake manifold are actuated with electric actuators or vacuum actuators. Each of the two types of actuators has several disadvantages. For example, an electric actuator is relatively expansive and difficult to accommodate in a tightly-packed engine compartment of a vehicle. A vacuum actuator requires a vacuum tank, which is also difficult to accommodate in an engine compartment.